The invention relates to novel optically active oxazoline compounds represented by the formula (I): ##STR2## as well as liquid crystal compositions containing them and an optical switching method using them.
So far, conventional liquid crystals have widely been used as materials for display devices. In most cases, these display devices are based on Twisted Nematic (hereinafter, referred to as "TN") mode using nematic liquid crystals, so that they have a disadvantage that almost all the response speeds of them are extremely low, namely, as slow as several milliseconds at the fastest.
In order to eliminate this disadvantage of TN mode, various attempts have been made. For example, a display method using a ferroelectric liquid crystal is disclosed in N. A. Clarks et al., Applied phys. Lett. 36, 899 (1980). This method uses chiral smectic phase, particularly chiral smectic C phase, liquid crystal and attracts attention as a material for a high speed optical switching. Some ferroelectric liquid crystal materials using this principle have already been known [for example, refer to Japanese Patent Application Laid Open No. 70,455 [1989]. However, no material having satisfactory properties has been known yet.
The present inventors have studied intensively in order to develope a liquid crystal having satisfactory properties to be used for an optical switching method. Finally, they have found that the oxazoline compounds represented by the formula (I) satisfies the requirements. The invention has been completed based on this finding.